The present invention is directed to a printer synchronization control. In particular, the invention is directed to a synchronization control for maintaining columnar alignment of dots in characters printed by a dot matrix printer.
In a dot matrix printer, characters are printed on paper by selectively printing dots in a matrix arrangement. A shuttle is driven back and forth across the face of a paper or the like. Plural print elements are mounted on the shuttle. At preselected columnar positions on the paper, the print elements are caused to print a dot. A preselected arrangement of dots defines a character.
If the shuttle is driven at constant speeds back and forth across the paper, relatively cumbersome equipment is required to provide the forces necessary to repetitively stop and accelerate the shuttle. The relatively large forces required in utilizing such equipment results in considerable wear on the mechanical parts.
The magnitude of forces required in driving the shuttle can be substantially reduced by driving the shuttle at a non-uniform velocity. For example, the shuttle can be driven back and forth across the paper at a sinusoidally varying velocity. This allows relatively compact, low torque equipment to be used in replacement of the aforesaid cumbersome equipment. As a result, the wear on component parts is substantially reduced.
In such a printer, however, the dots produced by the print elements to define a character will not fall into columnar alignment. This is due to the constant flight times of the print elements and the varying shuttle velocity. The flight time of a print element is the time required for the element to impact the paper after being energized. The print element impacts the paper at preselected columnar positions of a character. The dots in a column are successively impacted as the shuttle alternately travels in opposite directions across the paper. Thus, although the flight time is constant, the print element traverses a columnar position on the paper at slightly different velocities as the shuttle reverses its direction of travel. This results in misalignment of the dots along a column of a character.
A primary advantage of the present invention is that it maintains the columnar alignment of dots in a character produced by a dot matrix printer wherein the shuttle is driven at non-uniform velocities back and forth across the paper.
Another advantage of the invention is that it permits the use of compact, low torque equipment in driving the shuttle.
Other advantages appear hereinafter.